Two-zone molten metal hydrogen-rich and carbon monoxide-rich gas generation process

ABSTRACT

A high pressure two-zone molten iron gasification process for converting solid, liquid and gaseous hydrocarbon feeds into separate substantially hydrogen-rich and carbon monoxide-rich streams at 2 to 200 atmospheres pressure by feeding hydrocarbons into the molten iron in a first zone ( 4 ) in which hydrogen-rich gas is formed and then circulating the molten iron into contact with an oxygen containing gas in a second zone ( 5 ) in which carbon monoxyide-rich gas is formed. The carbon level in the circulating molten iron is carefully controlled above 0.3 wt. % to minimize formation of FeO. Hydrogen sulfide and other volatile sulfur compounds are removed from the separate gas streams via scrubbing in downstream equipment ( 12  and  16 ).

This application is a Continuation-in-Part to U.S. Ser. No. 08/421,102,filed Apr. 13, 1995, now U.S. Pat. No. 5,577,346.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to, filed May 18, 1999, U.S. applicationSer. No. 09/308,523, and, May 18, 1999, U.S. application Ser. No.09/308,530.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates to a process of conversion of hydrocarbons viagasification into two high pressure gas streams: a hydrogen-rich streamand a carbon-monoxide-rich stream. More specifically, this inventionrelates to the use of a two-zone predominantly molten iron or molteniron alloy system in conjunction with the above gasification conversion.

II. Discussion of the Prior Art

Two-zone molten iron gasifiers are disclosed by:

U.S. Pat. No. 1,803,221 (1931) to Tyrer describes hydrogen-rich gasproduction by feeding methane or a methane-steam mixture into one molteniron zone below the surface of the metal, thereby assuring completereaction of the gaseous feed. The carbon which dissolves in the molteniron in the first zone is burned out of the molten iron in the secondzone with an oxygen containing gas. Additional oxygen containing gas maybe added to the combustion products leaving the second zone tocompletely oxidize to carbon dioxide any carbon monoxide remaining.

The disadvantages of the process described in this patent include:

The feedstocks are limited to hydrocarbon gases such as methane and donot include lower value hydrocarbon liquids or solids.

Operating pressure is nominally atmospheric pressure which is lesseconomical to operate than equipment producing hydrogen at elevatedpressures; two atmospheres and above.

The importance of controlling the carbon level in the molten iron is notconsidered and thus production of only lower purity hydrogen-rich gas ispossible. If a minimum carbon level of at least 0.3% is not maintained,excess iron oxide will form in the molten iron during oxidation and willbe converted to carbon monoxide and dilute the hydrogen-rich gas whenhydrocarbon feeds are introduced to the hydrogen-rich gas producingfirst zone.

U.S. Pat. Nos. 4,187,672 (1980) and 4,244,180 (1981) to Rasor describe ahydrocarbon gasification process in which solid hydrocarbons such ascoal are introduced on the surface of one molten iron bath zone in whichhigh temperature cracking of the hydrocarbons into lighter molecularweight materials takes place with residual carbon being dissolved in themolten iron. The cracked hydrocarbon products are removed via outlets inthe shaft through which the feed hydrocarbon solids enter the molteniron. The molten iron containing the carbon is transferred to the secondmolten iron zone in which an oxygen containing gas is introduced toconvert the carbon into carbon monoxide and raise the temperature of theiron for transfer back to the carbonization section. The carbon monoxideis further oxidized above the molten iron bath and the heat recoveredvia a boiler or similar system. Sulfur, if present in the feed, isremoved via slag formation on top of the molten iron. The disadvantagesof the process described in this patent include.

The feedstocks are limited to solid hydrocarbons such as coal and do notinclude lower value hydrocarbon liquids or gases.

Since the solid hydrocarbon feeds are introduced above the surface ofthe molten iron, cracking of the feeds occurs such that a very impurehydrogen gas stream is produced because of the presence of crackedhydrocarbon gases.

Since the product gas from the oxidation zone is further oxidized forenergy recovery in, for example, a steam boiler, no attempt is made toproduce a carbon monoxide-rich gas.

Sulfur removal from the solid feed via reaction with and removal of slagfrom the equipment is complicated and expensive.

Operating pressure is nominally atmospheric pressure, which is lesseconomical to operate that equipment producing hydrogen at elevatedpressures, two atmospheres and above.

The importance of controlling tile carbon level above 0.30% in themolten iron is not considered and thus production of only lower purityhydrogen-rich gas is possible.

U.S. Pat. No. 5,435,814 (1995) to Miller and Malone (Ashland) describesthe general concept of a two-zone molten iron system process operatingat high pressures, up to 100 atmospheres, with solid and liquid feedintroduction below the surface of the molten iron and production of ahydrogen-rich and carbon monoxide rich gas streams. The disadvantages ofthe process described in this patent include:

There is no method described for handling the feedstock sulfur.

The importance of controlling the carbon level in the molten iron is notconsidered and thus production of only lower purity hydrogen-rich gasmay be possible. The process is restricted to a particular method ofcirculating molten iron.

In summary, all of the above patents operate at atmospheric pressure anddo not control carbon at a minimum of 0.3% in molten iron. Furthermore,the Rasor patents do not inject feed below the surface of the molteniron and are restricted to solids feeds. Furthermore, all the patentsignore sulfur in the feed or use slag to remove it.

One-zone molten metal gasifiers are disclosed by:

U.S. Pat. No. 4,496,369 (1985) to Torneman and U,S. Pat No. 4,511,372(1985) to Axelsson in which coal or other liquid hydrocarbons areinjected advantageously below the surface of the molten iron along withoxygen and water vapor to form a mixed hydrogen and carbon monoxide gas.Iron oxides are also added to the molten iron to act as a coolant forthe melt. The primary objective of the invention is to produce gasifiedhydrocarbons and it is disclosed that production can be increased byoperating at high pressures. The high pressures are not only economicbecause of the reduced size of equipment but it is also disclosed thathigh pressure decreases the degree of refractory wear in the reactor andthe amount of dust carry-over in the gas from the reactor. In addition,it is disclosed that a higher sulfur level in the molten bath will alsoreduce the amount of dust carry-over from the reactor. The processdisclosed cites the advantage of maintaining the carbon content of thebath below 0.8% carbon to reduce the amount of dust carry-over from thereactor.

The primary disadvantage of the process described in this patent includethe lack of separate molten iron zones for gasification and thereby doesnot permit production of individual hydrogen-rich and carbonmonoxide-rich gas streams.

U.S. Pat. Nos. 4,574,714 and 4,602,574 (1986) to Bach and Nagel in whichsolid or liquid toxic and/or lower value hydrocarbons are injectedadvantageously below the surface of the molten iron alloy, along withoxygen specifically to destroy the toxic compounds. With appropriatefeeds a mixed hydrogen and carbon monoxide gas can be formed and C1chemistry may be utilized to advantage at times to produce usefulproducts. It is further disclosed that maintaining a carbon level of0.5-6% carbon, preferably 2-3% carbon in tile molten metal is desired toprevent refractory degradation and facilitate reaction kinetics byproviding a high concentration gradient for toxics destruction. Sulfur,when present in the feed, is removed via absorption in the slag. Thedisadvantages of the process described in this patent include.

The feedstocks are introduced to the molten iron single zone system fordestruction as hazardous materials and not to produce hydrogen-rich orcarbon monoxide-rich gases and thereby misses the advantages of feedingnon-hazardous feedstocks.

Sulfur removal from the solid feed via reaction with and removal of slagfrom the equipment is complicated and expensive.

Operating pressure is nominally atmospheric, which is less economical tooperate than equipment producing gases at elevated pressures; twoatmospheres and above. Also, rotating gasification vessels on trunnionsfor slag removal makes operating at higher pressures impractical.

The importance of controlling the carbon level in the molten iron atmore than 0.3% is not considered and thus production of only lowerpurity hydrogen-rich gas is possible.

The primary disadvantage of the process described in this patent includethe lack of separate molten iron zones for gasification and thereby doesnot permit production of individual hydrogen-rich and carbonmonoxide-rich gas streams.

The following foreign patents also disclose processes related to that ofthis application.

U.K. Patent 1,187,782 (1970) to Nixon discloses a reactor in which ahydrocarbon is introduced to one zone resulting in the production of ahydrogen-rich gas and oxygen is introduced into a second zone where thecarbon which was dissolved in the first zone is burned with oxygen togive the exothermic heat to maintain the appropriate temperature in thefirst zone. It is noted that the two zone system as described has anadvantage over hydrogen production in a single zone system which isoperated in “blocked out” operations equivalent to that of a two zonesystem. It is further disclosed that sulfur present in the iron may beremoved, purifying to some extent the iron. The disadvantages of theprocess described in this patent include:

Since no attempt is made to produce a carbon monoxide-rich gas in theoxidation zone, only a hydrogen-rich gas stream is produced.

Operating pressure is nominally atmospheric pressure, which is lesseconomical to operate than equipment producing hydrogen at elevatedpressures; two atmospheres and above.

The importance of controlling the carbon level above 0.3% in the molteniron is not considered and thus production of only lower purityhydrogen-rich gas is possible.

One embodiment of U.K. Patent 1,437,750 (1976) to Agarwal and Ahnerdescribes producing a combustible gas containing a ratio of hydrogen tocarbon monoxide of between 2:5 to 10:1 using a two-zone molten ironreactor with a coal feed to the top of one zone. Although the gases areproduced in separate zones after further conversion with, for example,the water gas shift reaction, they are combined so the product from thesystem is a single combustible gas. Carbon concentrations in the molteniron are between 1 and 3% in the first zone and between 3 and 5% in thesecond zone. The disadvantages of the process described in this patentinclude:

The feedstocks are limited to solid hydrocarbons such as coal and do notinclude lower value hydrocarbon liquids or gases.

Since the solid hydrocarbon feeds are introduced above the surface ofthe molten iron, cracking of the feeds occurs such that a very impurehydrogen gas stream is produced because of the presence of crackedhydrocarbon gases.

Since the product gas from the oxidation zone is combined with the gasfrom the first zone, no attempt is made to produce a carbonmonoxide-rich gas.

No disclosure is made concerning sulfur removal from the solid feed viareaction in the molten metal zones.

Operating pressure is nominally atmospheric pressure, which is lesseconomical to operate that equipment producing hydrogen at elevatedpressures, two atmospheres and above.

U.K. Patent 2,189,504 (1987) to Herforth describes a two-zone molteniron reactor in which low grade solids fuels are gasified in one zoneand high grade solid fuels are gasified in the second zone. This permitsthe low grade solid fuels and waste materials to be consumed and producea low quality off-gas where as the gasification of high grade fuels inthe second zone permits production of a high quality off-gas unmixedwith the low quality off-gas while still permitting destruction of thelow grade fuels or waste materials. The sulfur is removed in the slagformed in the reactors. The disadvantages of the process described inthis patent include:

The feedstocks are limited to solid hydrocarbons such as coal and do notinclude lower value hydrocarbon liquids or gases.

Since the solid hydrocarbon feeds are introduced above the surface ofthe molten iron, cracking of the feeds occurs such that a very impurehydrogen gas stream is produced because of the presence of crackedhydrocarbon gases.

No attempts are made to produce either a hydrogen-rich or carbonmonoxide-rich off-gas.

Sulfur removal from the solid feed via reaction with and removal of slagfrom the equipment is complicated and expensive.

Operating pressure is nominally atmospheric pressure, which is lesseconomical to operate that equipment producing hydrogen at elevatedpressures; two atmospheres and above.

French Patent 2,186,524 (1974) to Vayssiere describes a two-zone molteniron system with a hydrogen-rich gas generated from hydrocarbonsinjected beneath the surface of the molten iron in one zone and either acarbon monoxide-rich gas or mixture of hydrogen and carbon monoxide gasgenerated by injecting oxygen or oxygen and hydrocarbon into the secondzone. The disadvantages of the process described in this patent include:

There is no provision for removal of the sulfur in the feed.

Operating pressure is atmospheric pressure, which is less economical tooperate that equipment producing gases at elevated pressures; twoatmospheres and above.

The importance of controlling the carbon level above 0.3% in the molteniron is not considered.

In summary, while such systems referenced above may provide reasonableresults, none of them effect the production of a separate hydrogen-richstream and a separate carbon monoxide-rich stream at elevated pressuresby feeding hydrocarbons below the surface of the molten iron and withcontrolled carbon contents of the molten metal above 0.3%. Furthermore,these systems either have no provision for handling feed sulfur or use acomplicated and costly slag technique for sulfur removal. Sulfur capturein the slag requires slagging materials to be added to the molten metalzones and a more complicated means of regularly drawing off the sulfurcontaining slag. When sulfur is captured in slag the slag must then bedisposed of, typically in uneconomic and environmentally unsoundlandfills.

Thus, our survey of prior practices indicates that the prior art has notcombined the use of two zone molten iron gasifiers for separatehydrogen-rich and carbon monoxide-rich gas production, feed introductionbelow the molten iron surface, high pressure operation and carboncontent control of the molten iron in the manner we have.

SUMMARY OF THE INVENTION

Broadly, this invention involves a process for producing in separatestreams a hydrogen-rich gas and a carbon monoxide-rich gas from twomolten metal zones and necessary ancillary equipment. Molten metalcomponents are intended to include any molten material layer within aparticular zone; e.g., molten metals, such as iron and its alloys, whichare always present and slag components, if present, that would form asecond molten layer with such molten metals. The molten metal employedin this invention is preferably molten iron but may be copper, zinc,especially chromium, manganese, or nickel, or other meltable metal inwhich carbon is somewhat soluble and which is at least 50% molten ironby weight.

In the first molten metal zone, a hydrocarbon feed in the form of arelatively dry gas or liquid or solid or solid-liquid slurry or atomizedsolid or liquid is fed beneath the molten metal surface and ahydrogen-rich gas is produced. By relatively dry is meant below 1% byweight of water. By introducing the feed below the surface of the moltenmetal substantially complete chemical reactions and conversions tohydrogen and carbon of the feed can be achieved. The carbon in thehydrocarbon feed dissolves in the molten metal.

In the second molten metal zone, into which molten metal from the firstmolten metal zone flows, all oxygen bearing stream is introduced toconvert the carbon dissolved in the molten metal from the first zoneinto a carbon monoxide-rich gas stream which exits from above the moltenmetal bath in a gas stream separate from the hydrogen-rich gas streamfrom the first molten metal zone. Molten metal from which the carbon hasbeen gasified by oxygen in the second zone is returned to the firstmolten metal zone.

Both molten metal zones are operated at elevated pressures, above twoatmospheres, to reduce the size of the equipment need to produce andfurther treat, if necessary, the hydrogen-rich and carbon-monoxide richgases. In addition, as disclosed is U.S. Pat. No. 4,511,372 incorporatedby reference, operation at high pressures reduces dust carry over andwear on refractory walls of the vessel. Furthermore, the capital andoperating costs of compression, of these gases to pressures at whichthey are utilized commercially are eliminated or substantially reduced.

Furthermore, in this process the amount of carbon in the molten iron towhich the hydrocarbon feed is introduced is carefully controlled toabove 0.3% to minimize formation of high levels of FeO, ferrous oxide,which could include a separate FeO phase. High levels of FeO will reactwith the carbon in the hydrocarbon feed and produce high levels ofcarbon monoxide, thereby contaminating the hydrogen-rich stream. If aseparate phase of FeO is present it will attack the refractory of thevessels holding the molten iron. The amount of carbon in the molten ironshould not normally exceed an tipper limit as determined by itssolubility in molten iron.

This invention also includes having the hydrogen-rich and carbonmonoxide-rich gases flowing from die molten metal zones through separateproduct gas lines to pass through successive downstream coolers,scrubbers or other gaseous impurity removal devices, and knock-out drumsto cool the gases and to remove any solids and any condensed liquidsfrom the gas streams. The gases may further be fed to proven scrubberswhich remove hydrogen sulfide and other volatile sulfur compoundsproduced in the molten metal zones and emit a substantially sulfur-freeand carbon oxide-free hydrogen-rich product gas and a substantiallysulfur-free carbon monoxide-rich product gas.

Suitable feeds for the process include carbonaceous reactant feedstocksselected from the group consisting of: light gaseous hydrocarbons suchas methane, ethane, propane, butane, natural gas, and refinery gas;heavier liquid hydrocarbons such as naphtha, kerosene, asphalt,hydrocarbon residua produced by distillation or other treatment of crudeoil, fuel oil, cycle oil, slurry oil, gas oil, heavy crude oil, pitch,coal tars, coal distillates, natural tar, crude bottoms, and usedcrankcase oil; solid hydrocarbon such as coal, rubber, tar sand, oilshale, and hydrocarbon polymers; and mixtures of the foregoing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of the basic process of this invention.

FIG. 2 is a drawing of a variation of the process of this inventionincorporating scrubbing systems to remove hydrogen sulfide and othervolatile sulfur compounds from the hydrogen-rich and carbonmonooxide-rich gases made in the process.

FIG. 3 is a drawing of a variation of the process of this inventionincorporating the use of feed and product valving systems to/from twomolten metal reactors to duplicate the effect of creating two moltenmetal zones separately by feed and product control systems instead oftransferring the molten metal between two zones of a single reactors

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates the invention in a simplified diagram of allapparatus for carrying out the basic process. Molten iron 2 is containedin the vessel 1. The molten iron in vessel 1 is maintained at atemperature of 1200-2500° C. between 1150° and 1750° C. (2102°-3182° F.)to keep it substantially liquid. Partition 3 divides the vessel into twozones 4 and 5. A hydrocarbon feed in the form of a relatively dry liquidor solid or solid-liquid slurry or atomized solid or liquid in a gas isfed through tuyere pipe 6 or lance pipe 7 beneath the molten metalsurface of zone 4 in which the hydrocarbon is converted to ahydrogen-rich gas which escapes from the surface of the molten metal andcarbon which dissolves in the molten metal. The hydrogen-rich gas exitszone 4 via pipe 10 and enters a cooling system 11 where it is cooled totemperatures suitable for its introduction into commercial hydrogen-richgas consuming processes suitable equipment for controlling the pressureabove 2 atmospheres (e.g. 2-2000 atmospheres) is provided before thehydrogen-rich gas is sent to a consuming process via pipe 13. Molteniron containing dissolved carbon from zone 4 is transferred to zone 5and oxygen is introduced beneath the molten metal surface in zone 5through tuyere pipe 8 or lance pipe 9. The carbon in the molten iron inzone 5 is converted to a carbon monoxide-rich gas in zone 5 and exitsthe vessel via pipe 14 and enters a cooling system 15 where it is cooledto temperatures suitable for its introduction into commercial carbonmonoxide-rich gas consuming processes. Suitable equipment forcontrolling the pressure above 2 atmospheres is provided before thecarbon-monoxide-rich gas is sent to a consuming process via pipe 17.

The following additional features characterize the process illustratedin FIG. 1:

Suitable feeds for the process introduced via tuyere pipe 6 or lancepipe 7 include carbonaceous reactant feedstocks selected from the groupconsisting of: light gaseous hydrocarbons such as methane, ethane,propane, butane, natural gas, and refinery gas; heavier liquidhydrocarbons such as naphtha, kerosene, asphalt, hydrocarbon residuaproduced by distillation or other treatment of crude oil, fuel oil,cycle oil, slurry oil, gas oil, heavy crude oil, pitch, coal tars, coaldistillates, natural tar, crude bottoms, and used crankcase oil; solidhydrocarbon such as coal, rubber, tar sand, oil shale, and hydrocarbonpolymers; and mixtures of the foregoing.

If the feeds introduced via tuyere pipe 6 or lance pipe 7 includesulfur, the sulfur will be removed from the system via its capture in aslag floating on the molten iron in zones 4 and 5. Or the sulfur willremain as hydrogen sulfide or other volatile sulfur compounds in thehydrogen-rich and carbon monoxide-rich gas streams and go to the gasconsuming processes via pipes 13 and 17.

Any dust and fume generated as part of the process in zones 4 and 5 willbe removed from the hydrogen-rich and carbon monoxide-rich gas streamsvia conventional means such as bag filters which are part of the gascooling systems 11 and 15.

The amount of carbon in the molten iron which is returned to zone 4 fromzone 5 to which the hydrocarbon feed is introduced is carefullycontrolled to above 0.3% at all times to minimize formation of aseparate phase of FeO, ferrous oxide. If present in substantial amounts,the FeO will react with the carbon in the hydrocarbon feed entering viatuyere pipe 6 or lance pipe 7 and produce carbon monoxide therebydiluting the hydrogen-rich stream exiting zone 4 via pipe 10. Inaddition, FeO in a separate phase will attack the refractory lining ofvessels holding the molten iron. The amount of carbon in the molten ironwhich passes from zone 4 to zone 5 should not normally exceed an upperlimit as set by the solubility of carbon in molten iron.

The molten metal employed in this invention as bath 2 is preferably andpredominantly molten iron but may be copper, zinc, especially chromium,manganese, or nickel, or other meltable metal in which carbon issomewhat soluble but is at all times at least 50 wt. % molten iron.

FIG. 2 is drawing of a variation of the basic process. In addition toincorporating all the elements of FIG. 1 including the descriptionabove, in this variation the sulfur in the feed is allowed to build tipto equilibrium levels in the molten metal and slag in zones 4 and 5. Atequilibrium, the sulfur compounds in the slag and metals will beconverted to hydrogen sulfide and other volatile sulfur compounds inzones 4 and 5 and exit in the hydrogen-rich and carbon monoxide-richgases via lines 10 and 14. After cooling in systems 11 and 15 the sulfurcompounds are removed from the gases by conventional means such as aminescrubbing, caustic scrubbing, or other suitable sulfur compound removingdevices, etc. in sulfur removal systems 12 and 16 before the nowessentially sulfur-free gases enter the gas consuming processes viapipes 13 and 17. The advantage of this mode of operation is a reducedproduction of slag and reduced dust formation as shown in the prior art,U.S. Pat. No. 4,511,372 which is hereby incorporated by reference.

FIG. 3 is a drawing of another variation of the process incorporationall of the applicable descriptions of FIGS. 1 and 2 and incorporatingthe use of feed and product valving systems to/from two molten metalreactors to duplicate the effect of creating two molten metal zonesseparated by feed and product control systems instead of transferringthe molten metal between two zones of a single reactor.

In this variation, as shown in FIG. 3, the process comprises two (ormore) identical systems performing functions comparable to the systemsin FIGS. 1 and 2 and including: vessels 11 and 21 holding molten iron inbaths 12 and 22; feed tuyere pipes 16 and 26 and alternative feed lancepipes 17 and 27 for introducing hydrocarbon feeds below the surface ofthe molten iron 12 and 22; feed tuyere pipes 18 and 28 and alternativefeed lance pipes 19 and 29 for introducing oxygen below the surface ofthe molten iron 12 and 22; vessel exit pipes 10 and 20; gas coolingsystems 13 and 23; and product gas pipes 60 and 50.

This system duplicates the two-zone reactor system of FIGS. 1 and 2 bycreating the equivalent of two zones with the use of suitable valves andcontrol systems on the feeds to vessels 11 and 21 and the product gasesexiting the cooling systems 13 and 23 via pipes 60 and 50. Thus, thecontrol systems are operated such that while hydrogen-rich gas is beingmade in vessel 11 and carbon monoxide-rich gas is being made in vessel21. After an appropriate length of time operating in this mode the feedand product control systems switches the feeds and products andhydrogen-rich gas is made in vessel 21 and carbon monoxide-rich gas ismade in vessel 11. The hydrocarbon feed system is described as follows:hydrocarbons are conducted to the system in pipe 40 which divides intopipes 41 and 44; pipe 49 leads to valve 42 and pipe 43 which isconnected to tuyere pipe 26 or lance pipe 27 in vessel 21; pipe 44 leadsto valve 45 and pipe 46 which is connected to tuyere pipe 16 or lancepipe 17 in vessel 11. The oxygen feed system is described as follows:oxygen is conducted to the system in pipe 30 which divides into pipes 31and 34; pipe 31 leads to valve 32 and pipe 33 which is connected totuyere pipe 28 or lance pipe 29 in vessel 21; pipe 34 leads to valve 35and pipe 36 which is connected to tuyere pipe 18 or lance pipe 19 invessel 11. The determination of whether hydrocarbons or oxygen are fedto either vessel 11 or 21 is determined by whether valves 32, 35, 42 and45 are open or shut; these settings, in turn, being established by thecontrol system.

The product gas systems from vessel 11 is described as follows: productgases exit vessel 11 via pipe 10, pass through cooling system 13 andenter pipe 60; the gases may then go via pipe 61 through valve 62 intopipe 63 amid pipe 54 connecting with the commercial processes usinghydrogen-rich gas; or the gases may go via pipe 65 through valve 66 intopipe 67 and pipe 58 connecting with the commercial processes usingcarbon monoxide-rich gas. The product gas systems from vessel 21 isdescribed as follows: product gases exit vessel 21 via pipe 20, passthrough cooling system 23 and enter pipe 50; the gases may then go viapipe 51 through valve 52 into pipe 53 and pipe 54 connecting with thecommercial processes using hydrogen-rich gas; or the gases may go viapipe 55 through valve 56 into pipe 57 and pipe 58 connecting with thecommercial processes using carbon monoxide-rich gas. The routing of eachgas is determined by whether valves 62, 66, 52 and 56 are open or shut;these settings, in turn, being established by the control system.

As an example of the operation of the system in FIG. 3, if hydrogen-richgas were being produced in vessel 11 and carbon monoxide-rich gas werebeing produced in vessel 21, the following valves would be open; 45, 32,62, 56, and closed; 42, 35, 66, 52. These valve settings would bereversed when hydrogen-rich gas were being produced in vessel 21 andcarbon monoxide-rich gas were being produced in vessel 11. The systemfor FIG. 3 has been described in simple terms for the general concept. Amore detailed description of the operation is given in U.S. Ser. No.08/425,938, filed Apr. 19, 1995, which is incorporated by reference.This application also describes the use of three molten metal vessels,instead of two, with a similar valving and control system to permitcontinuous gasification operations when one reactor must be out ofservice for repairs, etc. This feature is also included in the presentdisclosure by reference.

Another variation of the process is to use an oxygen enriched gas as thesource of oxygen through tuyere pipe 8 or lance pipe 9 (FIGS. 1 and 2)for gasifying the dissolved carbon in the molten metal in zone 5.

Another variation of the process is to use liquid feedstocks prior totheir introduction to the system via tuyere pipe 6 or lance pipe 7 as ascrubbing medium in the cooling sections 11 and 15 for dust and fumeremoval from the hydrogen-rich and carbon monoxide-rich product gasesexiting vessel 1 through pipes 10 and 14 (FIGS. 1 and 2).

Another variation of the process is to use a quantity of hydrogen-richgas from pipe 13 (FIGS. 1 and 2) or elsewhere in the system to atomizeliquid hydrocarbon feeds as they are introduced to zone 4 via tuyerepipe 6 or lance pipe 7.

Another variation of the process is to use a quantity of carbonmonoxide-rich gas pipe 17 (FIGS. 1 and 2) or elsewhere in the system tocool tuyere pipe 8 or lance pipe 9 introducing the oxygen to the moltenmetal in zone 5.

Another variation of the process is to use a quantity of water vapor orsteam to cool tuyere pipe 8 or lance pipe 9 introducing the oxygen tothe molten metal in zone 5 and to moderate the temperature in zone 5.

Another variation of the process is to use a quantity of carbon dioxidegas to cool tuyere pipe 8 or lance pipe 9 introducing the oxygen to themolten metal in zone 5 and to moderate the temperature in zone 5.

Another variation of the process is to use a quantity of methane gas tocool tuyere pipe 6 or lance pipe 7 introducing the feed to the moltenmetal in zone 4 and to moderate the temperature in zone 4.

The following explanation details the importance to this invention ofcontrolling the amount of oxygen introduced to the carbon monoxide-richgas generation section such that the carbon content of the molten ironreturned to the hydrogen-rich gas generation section is above a minimumvalue and thereby ensures that the hydrogen-rich gas contains a minimumof impurities. It also emphasizes the importance of these controlsparticularly when operating at the high pressures of this invention.Reference (by page number and/or figure number) are made to the data inthe book, “The Making, Shaping and Treating of Steel”, Tenth Edition,Copyright 1985 by Association of Iron and Steel Engineers.

The desired primary chemical reaction taking place in the hydrogen-richgas generation section of this invention involves the gasification of ahydrocarbon feed (CH_(n)):

CH_(n)=n/2H₂(hydrogen gas)+C−Fe (carbon dissolved in molten iron)  (1)

However, two important and undesirable secondary reactions will takeplace between the carbon in the feed and any oxygen and iron oxide (FeO)which is present in the molten iron:

C+O−Fe(oxygen dissolved in molten iron)=CO(carbon monoxidegas)+Fe(molten)  (2)

C+FeO(separate phase in molten iron)=CO(carbon monoxidegas)+Fe(molten)  (3)

Reactions (2) and (3) are undesirable since carbon monoxide gas isgenerated which dilutes the hydrogen gas produced by reaction (1) andthereby requires more extensive hydrogen-rich gas purificationfacilities. In addition, it is known that FeO in a separate phase willattack refractory linings of vessels holding molten iron to a greaterextent than just molten iron so that the conditions for Reaction 3 totake place should be minimized or eliminated, that is, there should beno separate FeO phase present with the molten iron.

Similarly, the desired chemical reaction taking place in the carbonmonoxide-rich gas generation section of the invention involves theoxidation of the carbon dissolved in the molten iron coming from thehydrogen-rich gas generation section:

2C−Fe(carbon dissolved in molten iron)+O₂=2CO+Fe(molten)  (4)

Again, there are two undesirable secondary reactions which take placebetween the iron and the oxygen fed to this section:

Fe+O₂=O−Fe(oxygen dissolved in molten iron)  (5)

2Fe+O₂=2FeO(separate phase in molten iron)  (6)

Note that the chemical elements shown in the above equations areillustrative of the materials involved and the processes taking placebut may not necessarily represent the actual molecular species which maybe present. For example, experimental evidence has shown that: a) oxygendissolved in molten iron may be present as dissolved FeO or in otheriron-oxygen ratios; b) carbon dissolved in molten iron may be present asdissolved FeC or in other iron/carbon ratios.

It is an important feature of this invention that the process must becontrolled based on a complete understanding of the factors whichcontrol the degree to which all the above reactions, and in particularthe secondary reactions (reactions 2, 3, 5, 6) will take place. Thefollowing quantitative relationships are critical to this understanding.

When oxygen and molten iron are present, oxygen is soluble to a limitedextent in molten iron; the maximum solubility being 0.16% at 1527° C.(2781° F.) (page 405 in reference). Graphically, the solubility ofoxygen at other temperatures is presented in FIG. 13-542 whilemathematically it is described by (page 406):

log[wt. % O]=−6320/T(°K)+2.734  (7)

If more oxygen is added to molten iron than will be soluble according tothe above, the oxygen reacts with the iron and a separate FeO phase isformed (page 405).

When oxygen and carbon and molten iron are present, the amount of oxygenin the molten iron as well as the amount of carbon in the molten ironare related according to the following reaction (page 674).

CO(pressure above molten iron)=O+C(concentrations in molten iron)  (8)

and equation

K=[wt. % C]×[wt. % O]/Pco (partial pressure CO, atm)  (9)

log K=−1168/T(°K)−2.07  (10)

The fact that the concentrations of carbon and oxygen dissolved inmolten iron are proportional to and affected by the partial pressure ofthe carbon monoxide above the molten iron is critical to the processcontrol and successful commercial application of this invention. Thistrend is illustrated by the following example.

According to Equation 7 the solubility of oxygen in molten iron at 1482°C. (2700° F.) is 0.136 wt. %. Thus, if more than 0.136 wt. % oxygen ispresent in the molten iron, it will be present as a separate phase ofFeO. According to Equation 9, the following amounts of oxygen will bepresent in molten iron at 1482° C. (2700° F.) when the molten ironcontains 0.3 wt. % and 4.5 wt. % carbon at various pressures of carbonmonoxide above the molten iron bath:

CO Pressure, psia wt. % O at 0.3% Carbon wt. % O at 4.5% Carbon 0.1470.000061 0.000004 1.47 0.000613 0.000041 14.7 0.00613 0.00041 294.00.1226 0.0082 485.1 0.2023 0.0135 735.0 0.3060 0.0204

It is observed that, when the CO pressure is at 485.1 or 735.0 psia andthe carbon in the molten iron is at 0.3 wt. %, the amount of oxygen ispresent in the molten iron is above 0.136 wt. % (the maximum solubilityof oxygen) and thus a separate FeO phase will also be present. These areconditions under which the carbon monoxide-rich section of the inventioncould be operated and would be the composition of the molten ironcirculated to the hydrogen-rich gas generation section. When circulatedback to the hydrogen-rich gas generation section the pressure of thecarbon monoxide would be minimum and the dissolved oxygen and FeO wouldreact be released as carbon monoxide into the hydrogen-rich gas byReactions 2 and 3 above and thereby dilute the hydrogen-rich gas. Inaddition the refractory holding the molten iron would be subject toattack by the FeO. Although, the amount of dissolved oxygen in themolten iron cannot be controlled, the amount of FeO as a separate phasecan by controlling the amount of carbon in the molten iron in the carbonmonoxide-rich gas generation section. This would be done by regulatingthe amount of oxygen introduced into the carbon monoxide-rich gasgeneration section such that the amount of carbon in the molten iron didnot fall below a specific prescribed level for the given operatingconditions. According to Equation 9 at 1482° C. (2700° F.) the amount ofcarbon in the molten iron to minimize the formation of a separate phaseof FeO should be above 0.446 wt. % at 485.1 psia and 0.676 wt. % at 735psia.

While using specific quantities for demonstration purposes, the aboveexample illustrates the trends involved in the control of the operationsof the invention but in no way limits the operating conditions to thoseshown. Other operating temperatures and pressures will determineappropriate carbon and oxygen content limitations for the molten iron.

What is claimed is:
 1. A process for generating both a hydrogen-rich gasstream and a carbon monoxide-rich gas stream at a pressure in the rangeof 2 to 200 atmospheres, said process comprising: a) introducing into afirst molten metal zone, containing molten metal of at least 50% molteniron by weight, operating at 1200°-2500° C. (2192°-4532° F.) and at 2 to200 atmospheres, a hydrocarbon feed in the form of a relatively dry,less than 1% by weight of water, gas or liquid or solid or solid-liquidslurry or atomized solid or liquid in a gas beneath the molten metalsurface of the zone in which the hydrocarbon is converted to ahydrogen-rich gas which escapes from the surface of the molten metal,and to carbon which dissolves in the molten metal; b) transferring atleast a portion of the molten metal of the first molten metal zone to asecond molten metal zone; reducing the carbon content of the moltenmetal of the second molten metal zone by adding a controlled amount ofan oxygen containing stream to oxidize carbon in the molten metal of thesecond molten metal zone and to produce a carbon monoxide-rich gasstream; c) recycling at least a portion of the molten metal of thesecond molten metal zone back to the first molten metal zone such thatthe amount of carbon in the molten iron which is returned to the firstzone from the second zone is controlled to be above 0.3 wt. % tominimize formation of a high level of FeO, ferrous oxide which highlevel causes formation of a separate phase of FeO or reaction withcarbon in the hydrocarbon feed; d) passing said separate hydrogen-richgas and carbon monoxide-rich gas streams out of their respective zonesand cooling them to temperatures suitable for their introduction intocommercial hydrogen-rich gas and carbon monoxide-rich gas consumingprocesses and controlling the pressure of each gas stream at above 2atmospheres; e) removing sulfur in the feed via its capture in a slagfloating on the molten iron in both zones or allowing the sulfur tobuild up to equilibrium levels in the molten iron and leave as hydrogensulfide or other volatile sulfur compounds in the hydrogen-rich andcarbon monoxide-rich gas streams; f) removing dust and fume generated aspart of the process in the molten metal zones generating thehydrogen-rich and carbon monoxide-rich gas streams via conventionalmeans which are part of a gas cooling system.
 2. The process as definedin claim 1 in which the molten metal is selected from the groupconsisting of iron, copper, zinc, chromium, manganese, and nickel. 3.The process as defined in claim 2 in which suitable feeds for theprocess include carbonaceous reactant feedstocks selected from the groupconsisting of: light gaseous hydrocarbons heavier liquid hydrocarbons;solid hydrocarbon and mixtures of the foregoing.
 4. The process asdefined in claim 1 in which all the sulfur in the feed is allowed tobuild up to equilibrium levels in the molten metal and slag zones atwhich point the sulfur compounds in the slag and metals will beconverted to hydrogen sulfide and other volatile sulfur compounds inmolten metal and slag zones and exit with the hydrogen-rich and carbonmonoxide-rich gases; and after cooling the sulfur compounds are removedfrom the gases by conventional means before the now essentiallysulfur-free gases pass to the commercial gas consuming processes.
 5. Theprocess as defined in claim 1 wherein each molten metal zone is withinan individual molten metal reactor.
 6. The process as defined in claim 1incorporating the use of an oxygen enriched gas as the source of oxygenfor oxidizing the dissolved carbon in the molten metal in the secondmolten metal zone.
 7. The process as defined in claim 1 wherein saidadding of a controlled amount of an oxygen containing stream is carriedout through a submerged lance entering the molten metal in the secondmolten metal zone through the top surface of molten metal of the secondmolten metal zone.
 8. The process as defined in claim 1 incorporatingthe use of liquid feed stocks prior to their introduction to the firstmolten metal zone as a scrubbing medium in the cooling for dust and fumeremoval from the hydrogen-rich and carbon monoxide-rich product gases.9. The process as defined in claim 1 incorporating the use of a quantityof hydrogen-rich gas to atomize liquid hydrocarbon feeds as they areintroduced into the first molten metal zone.
 10. The process as definedin claim 1 incorporating the use of a quantity of carbon monoxide-richgas to cool a tuyere pipe introducing said controlled amount of anoxygen-containing stream from below the molten metal surface of thesecond molten metal zone or a lance introducing said controlled amountof an oxygen-containing stream from above the molten metal surface ofthe second molten metal zone.
 11. The process as defined in claim 1incorporating the use of a quantity of water vapor or steam to cool atuyere pipe introducing said controlled amount of an oxygen-containingstream from below the molten metal surface in the second molten metalzone or a lance introducing said controlled amount of anoxygen-containing stream from above the molten metal surface in thesecond molten metal zone and to moderate the temperature in the secondmolten metal zone.
 12. The process as defined in claim 1 incorporatingthe use of a quantity of carbon dioxide gas to cool a tuyere pipeintroducing said controlled amount of an oxygen-containing stream frombelow the molten metal surface in the second molten metal zone or alance introducing said controlled amount of an oxygen-containing streamfrom above the molten metal surface in the second molten metal zone andto moderate the temperature in the second molten metal zone.
 13. Theprocess as defined in claim 1 incorporating the use of a quantity ofmethane gas to cool a tuyere pipe introducing the feed from below themolten metal surface in the first molten metal zone or a lanceintroducing the feed from above the molten metal surface in the firstmolten metal zone and to moderate the temperature in the first moltenmetal zone.
 14. The process as defined in claim 3 wherein said lightgaseous hydrocarbons are selected from the group consisting of methane,ethane, propane, butane, natural gas, and refinery gas; said heavierliquid hydrocarbons are selected from the group consisting of naphtha,kerosene, asphalt, hydrocarbon residua produced by distillation or othertreatment of crude oil, fuel oil, cycle oil, slurry oil, gas oil, heavycrude oil, pitch, coal tars, coal distillates, natural tar, crudebottoms, and used crankcase oil; and said solid hydrocarbon is selectedfrom the group consisting of coal, rubber, tar sand, oil shale, andhydrocarbon polymers.
 15. The process as defined in claim 4 wherein saidconventional means of removing sulfur compounds from said gases isselected from the group consisting of amine scrubbing and causticscrubbing.
 16. The process as defined in claim 1 wherein said adding ofa controlled amount of an oxygen containing stream is carried outthrough a tuyere pipe.
 17. The process as defined in claim 1 whereinsaid adding of a controlled amount of an oxygen containing stream iscarried out through a means selected from the group consisting of alance pipe and a tuyere pipe.
 18. The process of claim 1 wherein saidfirst molten metal zone operates at a temperature of 1482°-2500° C.(2700°-4532° F.).